Image courtesy of NCAR/EOL

From: Dr. Patrick Chuang
Iquique, Chile, November 8, 2008

Universal Time

The above picture is a satellite image of the VOCALS study region. Along the right side, about in the middle, it reads "IQQ" which is the location of Iquique. To the north is "ARI" or Arica, and to the south is Antofogasta. But what I want to point out to you is the time on the black bar across the top. After the date, which is November 3, 2008, the time reads: 14:15 UTC. What does this mean?

In large coordinated projects such as VOCALS, it's important that everybody's data has a time associated with it that other people can understand. There are usually two choices for time: the local time (what the people living there set their clocks to) and something called Coordinated Universal Time, which is abbreviated (slightly oddly) as UTC. UTC is (more or less) the solar time on the Prime Meridian, or 0 degrees longitude, which passes through Greenwich, England among other places. (Can you locate other places on the Prime Meridian using a map?)

So why is this useful? Since VOCALS scientists are making hundreds of different measurements from various ships, aircraft, satellites and on the ground, the easiest way to coordinate them all is to agree on using a common time. If everybody used local time, then my 11:25 a.m. might be someone else's 10:25 a.m. which might be a third person's 9:25 a.m. Using a common time avoids all of this confusion. It's not only scientists, though; for example, all airplanes worldwide only report time in UTC!

Here in Chile, the local clocks are 3 hours behind UTC. So if I wake up at 6 am, it's 9 am UTC. Can you figure out the difference between your local time zone and UTC? An Internet search might help you out here. The normal takeoff time for our airplane is 11 am UTC. What are you normally doing at that moment?



Postcards from the Field: Climate Science from the Southeast Pacific

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